This invention relates to a control unit incorporating a pressure sensor mounted to a printed circuit board which is housed in the control unit.
An example of detecting a pressure within an intake passage of a throttle body using a pressure sensor is disclosed in Japanese Utility Model Laid-Open Publication No. HEI-3-122246 entitled xe2x80x9cEngine Intake System.xe2x80x9d This pressure sensor is shown in FIGS. 6 and 7 hereof.
FIG. 6 illustrates an electronic control unit 101 incorporated in a throttle body 100.
The throttle body 100 includes a pressure sensor 102. The pressure sensor 102 has a pressure intake port 103 communicating with a pressure chamber 104. The pressure chamber 104 communicates with an intake passage 106 via a pressure passage 105. The pressure sensor 102 detects the pressure downstream of a throttle valve 107. The electronic control unit 101 controls the operating parameters of an engine (not shown), based on information on the pressure detected by the pressure sensor 102. The incorporation of the electronic control unit 101 in the throttle body 100 allows the pressure passage 105 to be formed within the throttle body 100.
In some cases, however, the electronic control unit 101 cannot be disposed in the vicinity of the throttle body 100 because of constraints on layout, for example. An example of such a case is described with reference to FIG. 7.
FIG. 7 shows an electronic control unit 111 disposed separately from a throttle body 110.
The electronic control unit 111 has a case 112 and a printed circuit board 113 provided within the case 112. A pressure sensor 114 is mounted on the printed circuit board 113. The pressure sensor 114 is connected to a hose connection 116 via a pressure-resistant hose 115.
A pressure hose 117 is connected to the hose connection 116 provided at a front end 112a (right end in the figure) of the case 112. The pressure hose 117 is communicated with an intake passage 118 of the throttle body 110 (downstream from a throttle valve 118a). A harness 120 is connected to a connecter 119 provided at a rear end 112b (left end in the figure) of the case 112. The electronic control unit 111 is connected to a battery and an actuator for controlling an engine.
The pressure sensor 114 detects the pressure in the intake passage 118 downstream from the throttle valve 118a. Based on information on the pressure detected by the pressure sensor 114, the electronic control unit 111 controls the actuator and controls the operating parameters of the engine.
However, the necessity of connecting the pressure sensor 114 of the electronic control unit 111 to the hose connection 116 via the pressure-resistant hose 115 results in an increased number of components.
In addition, the necessity of connecting one end of the pressure-resistant hose 115 to the pressure sensor 114 and connecting the other end of the pressure-resistant hose 115 to the hose connection 116 results in time-consuming assemblage and installation of the electronic control unit 111.
The increased number of components and the time-consuming assemblage and installation have prevented cost reduction of the electronic control unit 111.
To connect the harness 120 to the connector 119 provided at the rear end 112b of the case 112 requires supporting the case 112 with the right hand while connecting the harness 120 to the connector 119 with the left hand.
Also, the connection of the pressure hose 117 to the hose connection 116 provided at the front end 112a of the case 112 requires passing the case 112 to the left hand to connect the pressure hose 117 to the hose connection 116 with the right hand.
The necessity of passing the case 112 from the left hand to the right hand for connecting the pressure hose 117 after connecting the harness 120 results in the time-consuming assemblage and installation of the electronic control unit 111.
It is therefore an object of the present invention to provide a control unit incorporating a pressure sensor with a simplified and easy-to-assemble construction.
According to an aspect of the present invention, there is provided a control unit incorporating a pressure sensor, which comprises: a case body with an opening; a printed circuit board housed in the case body; a pressure sensor mounted on the printed circuit board and having a pressure intake pipe for taking in pressure from the outside; and a lid to close the opening of the case body, wherein the pressure intake pipe extends toward the lid, and the lid is integrally provided with a first pressure passage to which the pressure intake pipe is fitted, and a second pressure passage extending from the first pressure passage to the outside.
It is thus possible in the present control unit to fit the first pressure passage to the pressure intake pipe to communicate the pressure intake pipe with the second pressure passage via the first pressure passage, by placing the lid over the case body. This eliminates the need for a conventionally-used connecting hose, reducing the number of components to provide a simplified construction and thereby reduce the cost. Also, this saves the trouble of coupling the first pressure passage and the pressure sensor with a connecting hose, resulting in simplified assemblage.
In the present control unit, the case body has a box-like shape, and a connector box provided at one wall of four sidewalls of the case body, and the second pressure passage formed with the lid are oriented in the same direction. Thus the operation of connecting a harness to the connector box and the operation of connecting a pressure hose to the second pressure passage can be done from the same direction. That is, it is possible to connect the harness to the connector box with one hand while holding the control unit with the other hand and thereafter, without changing the hand holding the control unit, to connect the pressure hose to the second pressure passage. Further, the total length of the control unit can be made shorter as compared with a case where the connector box and the second pressure passage are oriented in opposite directions. This increases the degree of freedom in mounting space and facilitates the handling of the control unit during transportation.
In the present invention, the pressure sensor is disposed in the vicinity of the connector box. The thickness of the pressure sensor is generally greater than that of other resistive elements or the like on the printed circuit board. The thickness of the connector box is also generally greater than that of a plurality of control circuit components mounted on the printed circuit board. The maximum thickness of the control unit is determined by the thickness of the pressure sensor and the connector box. Technical difficulties in molding the lid increase as the second pressure passage integrally molded with the lid becomes longer. Under these considerations, the pressure sensor is disposed in the vicinity of the connector box. Such an arrangement of the pressure sensor and the connector box as the determinants of the maximum thickness of the control unit results in only a single portion of the control unit having a relatively large thickness. This facilitates the designing of the control unit. The disposition of the pressure sensor in the vicinity of the connector box makes the first pressure passage positioned above the pressure sensor, and shortens the second pressure passage communicating with the first pressure passage and extending in the same direction as the connector box. This also reduces the diameter of the second pressure passage, resulting in reduced technical difficulties in molding the lid.
An injection opening for the injection of molding resin into the control unit is provided in a corner of the lid in the most distant position from the pressure sensor. Since the pressure sensor has a large thickness as described above, it can prevent the flow of the molding resin. To eliminate this concern, the pressure sensor is disposed in a corner and the injection opening for the molding resin is provided in another corner of the lid which is most distant from the pressure sensor. This allows the smooth flow of the molding resin within the control unit when filling the inside of the control unit with the molding resin.